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Low PH test Kits??

Discussion in 'Water Chemistry' started by central tanks, May 1, 2017.

  1. central tanks

    central tanks Member

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    So iv been using API ph and high ph test kits for a long time. I just set up a 20 gal long black water tank and my ph measures 6 possibly lower(ph kit only tests down to 6.

    So what PH test kit do yall use for lower then 6ph aquariums? Please note no fish are in this tank, just set it up and ph was 6.6 with the tannin release and bacteria its droped.
  2. dw1305

    dw1305 Well-Known Member 5 Year Member

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    Hi all,
    I don't regularly measure pH, it isn't a very useful parameter in very soft water. I use conductivity and just keep it in the 60 - 120 microS range. If I kept black-water fish I'd aim for around 50microS.

    It is difficult to get an accurate pH measurement in very soft water, even with a fairly expensive electronic pH meter. If you have a neutral salt (like KCl) you can add this to your water sample to raise the electrical conductivity.

    Have a look at <"Test pH value in the low......">, it covers this area.

    One thing that people often don't realise is that pH won't be stable in very soft water.

    cheers Darrel
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  3. Mike Wise

    Mike Wise Moderator Staff Member 5 Year Member

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    Tetra used to sell a pH I (low range) test kit that went down to pH 4.7. I don't think it's sold now. I use a pH meter. If properly maintained it is a much less expensive option.
  4. central tanks

    central tanks Member

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    I have a ph meter and it is a hassle. I perform a 4.0ph cal and it reads 4ph, I perform the 7.0 ph cal and it reads a 7ph. I test my RO water that I know using liquid tests is a 6.6-6.8, but the damn metter reads a 7.6-8. Maybe I need to read the instructions again lol.
  5. central tanks

    central tanks Member

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    ya I know Ph wont be stable due to low dKH. knowing the ph is more of a mental thing for me. I full well expect it to shift slightly(slowely lower over time as nitrifying bacteria work and more tannins leach out). Water changes will keep it in the range I prefer as well as keeping the TDS in the level I want it. my TDS is around 120 and slowely rises to 130 over a week, I assume the extra 10 is coming from the elements in the sand, tank is 1 week old so im still working out the best maintenance routine to keep it at desired ranges. Im not keeping black water fish per say. Im going to keep Agazzisii which are black and white(clear) water fish. I just like the black water look personally.
  6. dw1305

    dw1305 Well-Known Member 5 Year Member

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    Hi all,
    Yes, that is it, you can't get a meaningful pH reading from RO water.

    When you use the pH4 and pH7 buffers, they are "buffers". This means they are special solutions made up from a conjugate base and acid that form a stable pH solution and resist changes to pH as acids (H+ ion donors) or bases (H+ ion acceptors) are added.

    I keep planted tanks, and even with water with some carbonate buffering, I'll get a pH rise during the day as the plants use CO2 (an acid) and evolve oxygen (a base).

    When you have RO water you have no buffering, and any small addition of bases, or acids, how ever small. causes a large swing in pH. You get the opposite effect with heavily carbonate buffered water (like Lake Tanganyika) where you need to add a large amount of acids to cause the pH to drop.

    cheers Darrel
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  7. Mike Wise

    Mike Wise Moderator Staff Member 5 Year Member

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    ... or just as likely from food added to the tank (and resulting waste products). 10 ppm TDS is rather minor.
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  8. central tanks

    central tanks Member

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    its a new tank so there is no fish, i did a test using a glass beaker. put water in and tested then added a handful of sand. About an hour later it was 10 tds higher. But it is a valid point to keep in mind that food and fish waste can even effect TDS (its obvious when you think about it yet iv never thought about or considered it.)

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